Various types of current control systems are available for ac motors. The present invention controller includes a current controlled inverter for converting variable dc power into ac phase power. For a three-phase ac drive mode, the inverter consists of six switches with two switches for each phase in totem pole arrangement such that the collector of the high side switch is connected to the dc link high, the emmiter of the low switch is connected to the dc link return and the junction is connected to the phase windings. The high speed transistor switches are alternately turned on and off based on a predetermined switching pattern.
Inversion is accomplished through a phase shift of the transistors to produce phase and line voltages displaced by 120.degree.. This three-phase output voltage is applied to the stator windings of the motor. In the conventional scheme, each transistor is turned "on" during an electrical-phase-and-rotation interval of 120.degree..
Various motor controllers have been designed to eliminate the disadvantages inherent in the conventional systems of this kind such as U.S. Pat. No. 4,547,719 which is designed to prevent adverse effects due to the dead zone of the pulse-modulation system and U.S. Pat. No. 4,761,599 which is intended to reduce electro-magnetic noise during forward rotation for a forward and reverse system. However, a need still exists for a system which can increase the power delivered to a motor from a given dc voltage supply. Also, a system which decreases the distortion of voltages and currents at high powers is very desirable.